While inserting this disclaimer into a book or movie may have the purpose of protecting the publisher or film company from lawsuits, it can also be a sneaky way of drawing attention to their product, like advertising. The promise that these actual events or similar ones actually occurred to someone somewhere adds a certain weight of authority to what otherwise would be a war story or courtroom drama perfectly indistinguishable from the rest of its fellows. After all, if it had happened before, maybe one day the very same thing could happen to you or someone you know. Which certainly makes this made-for-TV movie much more interesting doesn't it? The threat of truth is much more delicious than fiction. Fiction is cheap. Anyone can spew out fiction even if it is just brain diarrhea. Even Madonna does it. The truth is harder to fake.
Well, maybe not. Many of these little entertainments, especially movies, have sexed up the "true story" to appeal to audiences. This becomes a problem when the sensational Hollywood version becomes so popular that it clouds the original event that inspired it. Shows like U-571 took great liberties with history to play up America's role in the war. The audience comes away with a false impression of what really happened. While this tinkering makes it appealing to an American audience, it only strengthens jingoistic attitudes and does a grave disservice to the true heroes.